1. Field of the Invention
The present invention relates to a light source apparatus that supplies light to a light guide and an endoscope system including the light source apparatus.
2. Description of the Related Art
In light emitted by a light source apparatus that supplies light to a light guide, a light distribution (angular distribution) characteristic including not only a light intensity distribution characteristic but also an angular distribution characteristic is important. In other words, light source apparatuses are required to have not only a light condensing capability of efficiently connecting light from a light source to a light guide in order to ensure brightness of an endoscopic image, but also a wide light distribution characteristic of maintaining an intensity of a luminous flux having a large incident angle relative to a luminous flux in the vicinity of an optical axis of the luminous flux in order to ensure brightness of an outer peripheral portion of the endoscopic image.
In a light source apparatus for an endoscope, which is required to provide bight light, a discharge lamp such as a xenon lamp or a metal halide lamp is used as a light source lamp. However, in a light source lamp including a discharge lamp that includes an discharge electrode arranged on an optical path, the discharge electrode and a valve that includes the discharge electrode therein block light, resulting in occurrence of what is called a hollow defect in which a central region of an emitted luminous flux is darkened. Meanwhile, a light source lamp including a discharge lamp improved so as to emit brighter light, by means of reduction in diameter of, e.g., a discharge electrode, a valve and an opening of a reflector, emits a luminous flux whose quantity of light is larger in a central region than in a peripheral region.
In Japanese Patent Application Laid-Open Publication No. 2003-331622, the present applicant discloses a light source apparatus including an integrator portion. The integrator portion includes an entrance-side integrator lens, an exit-side integrator lens and a condensing lens for an integrator. Illuminating light entering the entrance-side integrator lens is divided into luminous fluxes with plural optical axes, and then is made to enter the opposed exit-side integrator lens, and the respective luminous fluxes are diffused there, and then combined substantially concentrically by the condensing lens for an integrator and emitted to the condensing lens side.